The present invention relates to fire-resistive polycarbonate resins, and more particularly, it relates to polycarbonate compositions which contain certain urazolates as fire-resistive agents and to methods for making fire-resistive polycarbonate resins.
The polycarbonate resins are already themselves self-extinguishing materials. Nevertheless, they are considered as still being too flammable for certain types of uses, particularly in the building industry, electric appliances, and in aerospace uses.
However, in order to make the polycarbonates more fire-resistant, a number of solutions have been suggested. Thus, the use of halogenated products, such as decabromodiphenylether, introduced as an additive, or tetrachloro- or tetrabromobisphenol A, condensed as copolymers with the polycarbonate, have already been used. However, the materials so obtained are liable to release hydrogen chloride or hydrogen bromide fumes, which are toxic and highly corrosive, during normal use or during fires.
The use of certain phosphorus derivatives, which do not entail such disadvantages, such as phosphonic esters of phenyl or xylyl acids having halogenated rings, have been suggested. Nevertheless, it is necessary to use quantities such that the mechanical properties of the polycarbonate so loaded and its ability to be worked are seriously affected. At the same time, the cost becomes prohibitive.
Some other additives, such alkaline salts of alkyl or arylsulfonic acids, have also been suggested, but the products obtained are usually translucent or opaque.